The components of variance for calibration methods of thin film CdTe photovoltaic modules

Methods for qualifying the performance of thin film CdTe modules are compared. The authors characterize short circuit current (I_sc) of two spectrally unique CdTe modules at STC using a class AAA indoor solar flash simulator and two calibration methods. In the first calibration method, two spectrally unique CdTe reference modules are established based on outdoor testing at STC and are used to calibrate the indoor flasher. In the second method, the spectral responses of two monitor cells and the two spectrally unique CdTe modules are used to calculate a total of four spectral mismatch factors per IEC 60904-7. Using the outdoor transfer calibration method, the authors find that regardless of which CdTe module is used to calibrate the indoor simulator the I_sc measurements deviate by 0.5% or less. The data from the mismatch factor approach show that the measured I_sc values deviate by an average of 1.1% depending on whether a KG3-filtered or an HOQ-unfiltered c-Si reference cell is used. Finally, the authors demonstrate that the largest source of variance between the two calibration methods is correlated to the primary reference cell calibration traceability.